idnits 2.17.1 draft-ietf-behave-nat64-discovery-heuristic-01.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (June 20, 2011) is 4692 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Behave WG T. Savolainen 3 Internet-Draft Nokia 4 Intended status: Standards Track J. Korhonen 5 Expires: December 22, 2011 Nokia Siemens Networks 6 June 20, 2011 8 Discovery of a Network-Specific NAT64 Prefix using a Well-Known Name 9 draft-ietf-behave-nat64-discovery-heuristic-01.txt 11 Abstract 13 This document describes a method for detecting presence of DNS64 and 14 for learning IPv6 prefix used for protocol translation on an access 15 network without explicit support from the access network. The method 16 depends on existence of a known IPv4-only domain name. The 17 information learned enables applications and hosts to perform local 18 IPv6 address synthesis and on dual-stack accesses avoid traversal 19 through NAT64. 21 Status of this Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on December 22, 2011. 38 Copyright Notice 40 Copyright (c) 2011 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 2. Requirements and Terminology . . . . . . . . . . . . . . . . . 3 57 2.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 3 58 2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 59 3. Host behavior . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 3.1. Connectivity test . . . . . . . . . . . . . . . . . . . . . 5 61 3.2. Non-standard IPv6 address formats . . . . . . . . . . . . . 6 62 4. Considerations for hosting the IPv4-only well-known name . . . 6 63 5. DNS(64) entity considerations . . . . . . . . . . . . . . . . . 6 64 6. Exit strategy . . . . . . . . . . . . . . . . . . . . . . . . . 6 65 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 66 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 67 8.1. About IPv4 address for the well-known name . . . . . . . . 7 68 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 69 10. Normative References . . . . . . . . . . . . . . . . . . . . . 7 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 72 1. Introduction 74 As part of the transition to IPv6 NAT64 [RFC6146] and DNS64 [RFC6147] 75 technologies will be utilized by some access networks to provide IPv4 76 connectivity for IPv6-only hosts. The DNS64 utilizes IPv6 address 77 synthesis to create local IPv6 presentations of peers having only 78 IPv4 addresses, hence allowing DNS-using IPv6-only hosts to 79 communicate with IPv4-only peers. 81 However, DNS64 cannot serve applications not using DNS, such as those 82 receiving IPv4 address literals as referrals. Such applications 83 could nevertheless be able to work through NAT64, provided they are 84 able to create locally valid IPv6 presentations of peers' IPv4 85 addresses. 87 Additionally, DNS64 is not able to do IPv6 address synthesis for 88 hosts running validating DNSSEC enabled resolvers, but instead the 89 synthetization must be done by the hosts. In order to perform IPv6 90 synthesis hosts have to learn the IPv6 prefix(es) used on the access 91 network for protocol translation. 93 This document describes a best effort method for advanced 94 applications and hosts to learn the information required to perform 95 local IPv6 address synthesis. An example application is a browser 96 encountering an IPv4 address literal in an IPv6-only access network. 97 Another example is a host running validating security aware DNS 98 resolver. 100 The knowledge of IPv6 address synthetization taking place may also be 101 useful if DNS64 and NAT64 are present in dual-stack enabled access 102 network. In such cases hosts may choose to prefer IPv4 in order to 103 avoid traversal through protocol translators. 105 The described method is intented for the scenarios where network 106 assisted NAT64 and prefix discovery solutions are not available. 108 2. Requirements and Terminology 110 2.1. Requirements 112 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 113 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 114 document are to be interpreted as described in [RFC2119]. 116 2.2. Terminology 118 Well-Known IPv4-only Name: a fully qualified domain name well-known 119 to have only A record. 121 Well-Known IPv4 Address: an IPv4 address that is well-known and 122 mapped to the well-known name. 124 3. Host behavior 126 A host requiring information about presence of NAT64 and the IPv6 127 prefix used for protocol translation shall send a DNS query for AAAA 128 records of a known IPv4-only fully qualified domain name. This may 129 happen, for example, at the moment the host is configured an IPv6 130 address of a DNS server. This may also happen at the time when first 131 DNS query for AAAA record is initiated. The host may perform this 132 check in both IPv6-only and dual-stack access networks. 134 When sending AAAA query for the known name a host MUST set "Checking 135 Disabled (CD)" bit to zero, as otherwise the DNS64 will not perform 136 IPv6 address synthesis hence does not reveal the IPv6 prefix(es) used 137 for protocol translation. 139 A DNS reply with one or more non-empty AAAA records indicates that 140 the access network is utilizing IPv6 address synthesis. A host MUST 141 look through all of the received AAAA records to collect all 142 available prefixes. The prefixes may include Well-Known Prefix or 143 one or more Network-Specific Prefixes. In the case of NSPs the host 144 SHALL search for the IPv4 address inside of the received IPv6 145 addresses to determine used address format. 147 An IPv4 address inside synthesized IPv6 address should be found at 148 some of the locations described in [RFC6052]. If the searched IPv4 149 address is not found on any of the standard locations the network 150 must be using different formatting. In such case the host may try to 151 find out the IPv4 address at some other location. 153 The host should ensure a 32-bit IPv4 address value is present only 154 once in an IPv6 address. In case another instance of the value is 155 found inside the IPv6, the host shall repeat the search with another 156 IPv4 address. 158 In the case only one IPv6 prefix was present in the DNS response: a 159 host shall use that IPv6 prefix for both local synthetization and for 160 detecting synthesis done by the DNS64 entity on the network. 162 In the case multiple IPv6 prefixes were present in the DNS response: 164 a host SHOULD use all received prefixes when determining whether 165 other received IPv6 addresses are synthetic. However, for selecting 166 prefix for the local IPv6 address synthesis host MUST use the 167 following prioritization order, of which purpose is to avoid use of 168 prefixes containing suffixes reserved for the future [RFC6052]: 170 1. Use NSP having /96 prefix 172 2. Use WKP prefix 174 3. Use longest available NSP prefix 176 In the case of NXDOMAIN or empty AAAA reply: the DNS64 is not 177 available on the access network, network filtered the well-known 178 query on purpose, or something went wrong in the DNS resolution. All 179 unsuccesful cases result in unavailability of a host to perform local 180 IPv6 address synthesis. The host MAY periodically resend AAAA query 181 to check if DNS64 has become available or temporary problem cleared. 182 The host MAY perform A query for the well-known name to learn whether 183 the service is available at all (see section 6 about Exit Strategy). 184 The host MAY also continue monitoring DNS replies with IPv6 addresses 185 constructed from WKP, in which case the host MAY use the WKP as if it 186 were learned during the query for well-known name. 188 To save Internet's resources, if possible, a host should perform 189 NAT64 discovery only when needed (e.g. when local synthesis is 190 required, cached reply timeouts, new network interface is started, 191 and so forth. Furthermore, the host SHOULD cache the replies it 192 receives and honor TTLs. 194 3.1. Connectivity test 196 After the host has obtained a candidate prefix and format for the 197 IPv6 address synthesis it may locally synthesize an IPv6 address, by 198 using a publicly routable IPv4 address, and test connectivity with 199 the resulting IPv6 address. The connectivity test may be conducted 200 e.g. with ICMPv6 or with a transport layer protocol. 202 This connectivity test ensures local address synthetization results 203 in functional and protocol translatable IPv6 addresses. 205 The host MUST NOT perform connectivity test for the well-known IPv4 206 address of the well-known name, but instead to some other destination 207 such as host vendor servers. 209 3.2. Non-standard IPv6 address formats 211 A node may need to perform more complex heuristics to cope with 212 networks possibly using non-standard IPv6 address formats. Non- 213 standard approaches might include for example: 215 1. Non-standard location: IPv4 address in one piece at non-standard 216 location. Can be found by pattern matching. 218 2. Fragmented: IPv4 address in multiple pieces around the IPv6 219 address. May be found by pattern matching. 221 3. Obfuscated address: IPv4 address is obfuscated, for example 222 xorred. May potentially be found especially if standard addess 223 format is used, but as this is an indication of access network's 224 unwillingness to support host based synthetization the host 225 should not try to decipher the IPv6 prefix. 227 4. Considerations for hosting the IPv4-only well-known name 229 The authoritative nameserver for the well-known name shall have DNS 230 record TTL set to a long value in order to improve effectiveness of 231 DNS caching. The exact value depends on availability time for the 232 used public IPv4 address, but should not be longer than one year. 234 5. DNS(64) entity considerations 236 DNS(64) servers MUST NOT interfere or perform special procedures for 237 the queries related to the well-known name until the time has arrived 238 for the exit strategy to be deployed. 240 6. Exit strategy 242 A day will come when this tool is no longer needed or is replaced by 243 some other tool. 245 In global scope the exit strategy includes sending NXDOMAIN replies 246 by the authoritative nameserver of the well-known name with very long 247 TTL. 249 In local scope, after network administrators have determined there is 250 no longer need for this tool in their network, they may start locally 251 serving A and AAAA queries for the well-known name with NXDOMAIN 252 reply. 254 A client implementation receiving NXDOMAIN for the AAAA query for the 255 well-known name is either not talking to DNS64 or this tool has been 256 disabled. NXDOMAIN response also for the A query for the well-known 257 name means this tool has been disabled. 259 7. Security Considerations 261 No security considerations have been identified. 263 8. IANA Considerations 265 A well-known name should be defined and a public IPv4 address 266 allocated (by IANA? IETF? Someone else?). 268 8.1. About IPv4 address for the well-known name 270 The global IPv4 address for the well-known, if possible, should be 271 chosen so that it is unlikely to appear more than once within an IPv6 272 address and also as easy as possible to find from within the 273 synthetic IPv6 address. A global address is required as otherwise 274 DNS64 entity will not perform AAAA record synthesis. The address 275 does not have to be routable as no communications are initiated to 276 the IPv4 address. 278 Allocating two IPv4 addresses would improve the heuristics in cases 279 where the primary IPv4 address' bit pattern appears more than once in 280 the synthetic IPv6 address (NSP prefix contains the same bit pattern 281 as the IPv4 address). 283 If no well-known IPv4 address is allocated for this method, the 284 heuristic requires sending additional A query to learn the IPv4 285 address that is sought inside the received IPv6 address. Without 286 knowing IPv4 address it is impossible to determine address format 287 used by DNS64. 289 9. Acknowledgements 291 Authors would like to thank Andrew Sullivan, Dan Wing, Washam Fan, 292 Cameron Byrne, and Christian Huitema for significant improvement 293 ideas and comments. 295 10. Normative References 297 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 298 Requirement Levels", BCP 14, RFC 2119, March 1997. 300 [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X. 301 Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, 302 October 2010. 304 [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful 305 NAT64: Network Address and Protocol Translation from IPv6 306 Clients to IPv4 Servers", RFC 6146, April 2011. 308 [RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van 309 Beijnum, "DNS64: DNS Extensions for Network Address 310 Translation from IPv6 Clients to IPv4 Servers", RFC 6147, 311 April 2011. 313 Authors' Addresses 315 Teemu Savolainen 316 Nokia 317 Hermiankatu 12 D 318 FI-33720 Tampere 319 Finland 321 Email: teemu.savolainen@nokia.com 323 Jouni Korhonen 324 Nokia Siemens Networks 325 Linnoitustie 6 326 FI-02600 Espoo 327 Finland 329 Email: jouni.nospam@gmail.com